1. Field of the Invention
The present invention relates to an information recording apparatus, and more particularly relates to an information recording apparatus for recording record information with respect to an information record medium such as an optical disc of write-once type onto which the record information can be written just once, or an optical disc of re-writable type onto which the record information can be repeatedly written.
2. Description of the Related Art
A CLV (Constant Linear Velocity) method of recording information at a constant linear velocity is employed as a recording format for the above described optical disc such as a DVD. Thus, at a time of reproducing the optical disc, a rotation control of a spindle motor is performed so as to obtain a rotation angular velocity, which is proportional to the radius from the inner circumferential side to the outer circumferential side. The CLV method is superior in that it can improve the recording density since the minimum readable pit can be recorded from the inner circumferential side to the outer circumferential side. In case of recording the information onto an optical disc of write once type such as a DVD-R (DVDxe2x80x94Recordable), the control according to the CLV method is also performed. Namely, the spindle motor is rotation-controlled so as to make the linear velocity constant, and the writing operation is performed while the various conditions such as a laser power etc. are set to be constant at an arbitrary position on the optical disc. At this time, the writing speed of the data per unit time (i.e., the channel bit rate) is constant, and the channel bit clock which defines this channel bit rate has a constant frequency.
By the way, when various contents are recorded with respect to the optical disc such as a DVD-R, it may be necessary to once interrupt or stop the writing process and perform a search. Namely, there may happen a condition in which the non-recorded recordable areas are dispersed over the whole area of the optical disc. In such a condition, the search is performed by largely moving the radial position of the optical pickup on the optical disc and the writing process is resumed (hereinafter, one series of actions including the writing process, the interruption of the writing process, the search and the resumption of the writing process is called as a xe2x80x9crecording sequencexe2x80x9d). By this, the flexibility or versatility of the arrangement in recording the information on the optical disc is improved, so that it is possible to efficiently record the contents.
However, as mentioned above, since the optical disc such as a DVD etc., employs the CLV method, it becomes necessary to perform the search by changing the radial position and change the rotation angular velocity of the optical disc so as to harmonize it with the radial position of the search destination, in correspondence with the distribution of the non-recorded recordable areas. Thus, a certain time duration is required in order to control the spindle motor to stably drive it at the search destination, so that the speedily search may not be performed. As a result, the time duration required for the recording sequence with respect to the optical disc is increased. And that, as the non-recorded recordable areas are more severely dispersed over the whole area of the optical disc, this tendency of increasing the time duration required for the recording sequence becomes stronger, which is a problem.
The present invention is proposed in view of the above mentioned problems. It is therefore an object of the present invention to provide an information recording apparatus, which can perform a recording operation with respect to the optical disc by the CLV method while controlling the laser power appropriately and rotation-controlling the optical disc at a constant rotation angular velocity, to thereby perform a speedily searching operation even during the recording sequence.
The above object of the present invention can be achieved by an information recording apparatus for recording record information onto an optical disc, which corresponds to a CLV (Constant Linear Velocity) method to keep a linear velocity of the optical disc constant when reproducing the record information from the optical disc. The information recording apparatus is provided with: an optical pickup having a laser for irradiating a light beam from the laser onto a record track of the optical disc and for detecting a reflected light from the optical disc; a rotation controlling device for rotation-controlling the optical disc to keep a rotation angular velocity of the optical disc constant when recording the record information onto the optical disc; and a laser drive controlling device for obtaining an optimum value of a laser driving amount for the optical pickup in correspondence with a linear velocity of the record track of the rotation-controlled optical disc with respect to the optical pickup and for drive-controlling the laser by use of the obtained optimum value of the laser driving amount.
According to the present invention, in case of recording the record information with respect to the optical disc corresponding to the CLV method in the information recording apparatus, the optical disc is rotation-controlled at the constant rotation angular velocity, the light beam emitted from the laser of the optical pickup is irradiated onto the record track, and the linear velocity at this time is obtained. Then, the power control for the laser is performed by use of the optimum value of the laser driving amount which is obtained in correspondence with this obtained linear velocity. By this, even if the relative linear velocity at the time of writing is changed depending upon the radial position of the optical disc, since the laser can be driven with the laser driving amount in such a level that the laser can appropriately write the record information onto the optical disc. Thus, it is possible to drive the optical disc without changing the rotation angular velocity and to perform a speedy searching operation in the recording sequence.
In one aspect of the information recording apparatus of the present invention, a wobble signal is recorded on the optical disc by wobbling the record track at a constant frequency, and the laser drive controlling device obtains the optimum value of the laser driving amount on the basis of a frequency of the wobble signal which is extracted from a detection output of the optical pickup.
According to this aspect, the frequency of the wobble signal recorded on the optical disc is extracted from the detection output in correspondence with the linear velocity when rotation-controlling the optical disc corresponding to the CLV method at the constant rotation angular velocity. Then, the optimum value of the laser driving amount is obtained on the basis of this frequency, and the power control for the laser is performed. By this, it is possible to obtain quite precisely the relative linear velocity at the time of writing without complicating the structure, and it is also possible to drive the laser while precisely and optimally controlling it, to thereby realize the speedy search in the recording sequence.
In another aspect of the information recording apparatus of the present invention, a pre-pit to which control information is recorded in advance is formed on a guide track of the optical disc, the information recording apparatus is further provided with a pre-pit detecting device for detecting the pre-pit, and the laser drive controlling device obtains the optimum value of the laser driving amount on the basis of an appearance interval of the detected pre-pit.
According to this aspect, by detecting the pre-pit, which is formed in advance on the guide track of the optical disc, in correspondence with the linear velocity when rotation-controlling the optical disc corresponding to the CLV method at the constant rotation angular velocity, the appearance interval of the pre-pit exhibiting a constant regularity is obtained. Then, the optimum value of the laser driving amount is obtained on the basis of this appearance interval and the power control for the laser is performed. By this, it is possible to obtain quite precisely the relative linear velocity at the time of writing without complicating the structure, and it is also possible to drive the laser while precisely and optimally controlling it, to thereby realize the speedy search in the recording sequence.
In another aspect of the information recording apparatus of the present invention, the rotation controlling device rotation-controls the optical disc to keep the rotation angular velocity of the optical disc at a predetermined rotation angular velocity for each of a plurality of division areas into which a whole recordable area of the optical disc is divided in a radial direction thereof, and the predetermined rotation angular velocity is set for each of the division areas individually such that the predetermined rotation angular velocity is smaller as a radial position of respective one of the division areas goes farther from an inner circumference to an outer circumference of the optical disc.
According to this aspect, the whole recordable area of the optical disc corresponding to the CLV method is divided in the radial direction into the division areas. The rotation control is performed at the constant rotation angular velocity, which is predetermined for each of the divisions areas individually such that the predetermined rotation angular velocity is smaller as the radial position of respective one of the division areas goes farther to the outer circumference. Then, the optimum value of the laser driving amount is obtained for each of the division areas in correspondence with this obtained linear velocity and the power control for the laser is performed. By this, since the changing range of the linear velocity is narrowed within each of the division areas, the variable range of the laser power is also narrowed within each of the division areas. Accordingly, it is possible to perform the laser driving control with low cost and by use of a rather simple structure, and it is also possible to perform the speedy search within the same division area within which the search is frequently performed.
The nature, utility, and further features of this invention will be more clearly apparent from the following detailed description with respect to preferred embodiments of the invention when read in conjunction with the accompanying drawings briefly described below.